Huperzine A is a plant alkaloid derived from the Chinese club moss plant, Huperzia serrata, which is a member of the Lycopodium species. Huperzia serrata has been used in Chinese folk medicine for the treatment of fevers and inflammation.

Huperzine A has been found to have acetylcholinesterase activity. Huperzine B, also derived from Huperzia serrata, is a much less potent acetylcholinesterase inhibitor. Natural huperzine A is a chiral molecule also called L-huperzine A or (-)-huperzine A. Synthetic huperzine A is a racemic mixture called (±)-huperzine A. Huperzine A is also known as HUP, hup A and selagine. In Chinese medicine, the extract of Huperzia serrata is known as Chien Tseng Ta and shuangyiping. Huperzine A derivatives are being developed for pharmaceutical application.

ACTIONS AND PHARMACOLOGY ACTIONS

Huperzine A may have cognition-enhancing activity in some.

MECHANISM OF ACTION

Alzheimer's disease is a neurodegenerative disorder associated with neuritic plaques that affect the cerebral cortex, amygdala and hippocampus. There is also neurotransmission damage in the brain. One of the major functional deficits in Alzheimer's disease is a hypofunction of cholinergic neurons. This leads to the cholinergic hypothesis of Alzheimer's disease and the rationale for strategies to increase acetylcholine in the brains of Alzheimer's disease patients. Two FDA-approved drugs for the treatment of Alzheimer's disease, tacrine and donepezil, are acetylcholinesterase inhibitors.

Huperzine A is also an acetylcholinesterase inhibitor and has been found to increase acetylcholine levels in the rat brain following its administration. It also increases norepinephrine and dopamine, but not serotonin levels. The natural L or (-)-huperzine A is approximately three times more potent than the racemic or (±)-huperzine A in vitro.

PHARMACOKINETICS

There are limited pharmacokinetic studies with huperzine A. It appears that huperzine A is rapidly absorbed from the gastrointestinal tract and transported to the liver via the portal circulation. Some first-pass metabolism takes place in the liver, and huperzine A and its metabolites are distributed widely in the body, including to the brain. Following ingestion, the time to reach peak blood level is approximately 80 minutes.

INDICATIONS AND USAGE

Huperzine A has potent pharmacological effects and, particularly since long-term safety has not been determined, it should only be used with medical supervision. It may have some effectiveness in Alzheimer's disease and age-related memory impairment. It has been used to treat fever and some inflammatory disorders, but there is no credible scientific evidence to support these uses.

RESEARCH SUMMARY

Numerous studies, most of them from China, suggest that huperzine A may be as effective as the drugs tacrine and donepezil in Alzheimer's disease. This is not so surprising since in vitro and animal model tests have demonstrated that huperzine A effectively inhibits acetylcholinesterase, an enzyme that catalyzes acetylcholine breakdown. Tacrine and donepezil work in the same way to conserve acetylcholine in the brain--the mode by which they presumptively improve memory and cognition in those with Alzheimer's and age-related cognitive impairment. Huperzine A may prove superior to tacrine (dose-limited due to its hepatotoxicity) if long-range studies, yet to be conducted, demonstrate its safety.

In one double-blind, randomized study, huperzine A, in injectable form, was tested against a saline control in 56 patients with multi-infarct dementia or senile dementia and in 104 patients with senile and pre-senile simple memory disorders. Huperzine A produced significant positive effects as measured by the Wechsler Memory Scale. Dizziness was experienced by a few of the huperzine A-treated patients.

In another study, this one multicenter, double-blind, placebo-controlled and randomized, 50 subjects with Alzheimer's disease were given huperzine A or placebo for eight weeks. Significant improvement was noted in 58 percent of the patients in terms of memory, cognitive and behavioral functions. Research is ongoing.

CONTRAINDICATIONS, PRECAUTIONS, ADVERSE REACTIONS CONTRAINDICATIONS

None known.

PRECAUTIONS

Huperzine A should be avoided by children, pregnant women and nursing mothers.

Because of possible adverse effects in those with seizure disorders, cardiac arrhythmias and asthma, those with these disorders should avoid huperzine A. Those with irritable bowel disease, inflammatory bowel disease and malabsorption syndromes should avoid huperzine A.

Acetylcholinesterase Inhibitors: Use of huperzine A along with the acetylcholinesterase inhibitors donepezil or tacrine may produce additive effects, including additive adverse effects. Other acetylcholinesterase inhibitors include neostigmine, physostigmine and pyridostigmine, and use of these agents along with huperzine A may produce additive effects, including additive adverse effects.

Cholinergic Drugs: Use of huperzine A along with cholinergic drugs, such as bethanechol, may produce additive effects, including additive adverse effects.

NUTRITIONAL SUPPLEMENTS

Use of huperzine A with choline, phosphatidylcholine, CDP-choline and L-alpha-glycerylphosphorylcholine hypothetically might produce additive effects, including additive adverse effects.

OVERDOSAGE

There are no reports of overdosage with huperzine A.

DOSAGE AND ADMINISTRATION

There are various forms of huperzine A available, including extracts of Huperzia serrata, natural (-)-huperzine A and synthetic racemic (±)-huperzine A. Natural (-)-huperzine A is approximately three times more potent than the synthetic racemic mixture. The doses of natural (-)-huperzine A used in clinical studies ranged from 60 micrograms to 200 micrograms daily. Huperzine A should only be used with a physician's recommendation and monitoring.

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